This invention relates to improved surfactant-solvent drying compositions which include a volatile solvent that has the capability of removing water or other aqueous films from the surface of substrates. Removal of the water from the substrate to be dried is effected by displacement; drying in this manner avoids an energy consuming drying step and, in the case of metals, avoids potential corrosion attendant after the use of aqueous cleaning methods.
Volatile solvent drying compositions used in the past have often proved less than satisfactory by failing to effectively displace water from the surface to be dried. To overcome this difficulty, in accordance with the invention, certain sarcosine surfactants have been found to provide highly advantageous results in promoting water displacement from surfaces that require drying.
An additional and serious problem encountered with varying severity in the use of solvent drying solutions, depending on the specific application and substrate to be dried, is the fact that such solutions tend to emulsify and are difficult to purify or to be freed of aqueous impurities so that the drying solution can be reused. The presence of emulsions in these drying compositions interferes with the free elimination of water, such as by decantation, and ultimately interrupts the water-displacement process which is the essential objective of the substrate drying treatment.
Various surfactants have been used to solve this problem of finding a good drying solvent while dealing effectively with the emulsification problem, with little success. For example, surfactants that do not cause emulsification usually dry poorly while good water-displacing surfactants usually cause emulsification of the displaced water.
It is thus apparent that a need exists for an effective solvent/surfactant surface drying system and, particularly, a system which is readily renewable by separating the water accumulated therein during use without encountering substantial interference by the presence of an emulsion phase.